Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / control-2.3.52 / __dss_bilin__.m

diff --git a/octave_packages/control-2.3.52/__dss_bilin__.m b/octave_packages/control-2.3.52/__dss_bilin__.m
new file mode 100644 (file)
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+++ b/octave_packages/control-2.3.52/__dss_bilin__.m
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+## Copyright (C) 2011   Lukas F. Reichlin
+##
+## This file is part of LTI Syncope.
+##
+## LTI Syncope is free software: you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## LTI Syncope is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with LTI Syncope.  If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## 1.  Discrete -> continuous
+## _
+## E = alpha*E + A
+## _
+## A = beta (A - alpha*E)
+## _
+## B = sqrt(2*alpha*beta) * B
+## _                                         -1
+## C = sqrt(2*alpha*beta) * C * (alpha*E + A)  * E
+## _                        -1
+## D = D - C * (alpha*E + A)  * B
+## 
+## 
+## 2.  Continuous -> discrete
+## _
+## E = beta*E - A
+## _
+## A = alpha (beta*E + A)
+## _
+## B = sqrt(2*alpha*beta) * B
+## _                                        -1
+## C = sqrt(2*alpha*beta) * C * (beta*E - A)  * E
+## _                       -1
+## D = D + C * (beta*E - A)  * B
+
+## Special thanks to Andras Varga for the formulae.
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: October 2011
+## Version: 0.1
+
+function [Ar, Br, Cr, Dr, Er] = __dss_bilin__ (A, B, C, D, E, beta, discrete)
+
+  if (discrete)
+    EpA = E + A;
+    s2b = sqrt (2*beta);
+    if (rcond (EpA) < eps)
+      error ("d2c: E+A singular");
+    endif
+    CiEpA = C / EpA;
+    
+    Er = EpA;
+    Ar = beta * (A - E);
+    Br = s2b * B;
+    Cr = s2b * CiEpA * E;
+    Dr = D - CiEpA * B;
+    
+    ## Er = E + A;
+    ## Ar = beta * (A - E);
+    ## Br = sqrt (2*beta) * B;
+    ## Cr = sqrt (2*beta) * C / (E + A) * E;
+    ## Dr = D - C / (E + A) * B;
+  else
+    bEmA = beta*E - A;
+    s2b = sqrt (2*beta);
+    if (rcond (bEmA) < eps)
+      error ("c2d: beta*E-A singular");
+    endif
+    CibEmA = C / bEmA;
+    
+    Er = bEmA;
+    Ar = beta*E + A;
+    Br = s2b * B;
+    Cr = s2b * CibEmA * E;
+    Dr = D + CibEmA * B;
+    
+    ## Er = beta*E - A;
+    ## Ar = beta*E + A;
+    ## Br = sqrt (2*beta) * B;
+    ## Cr = sqrt (2*beta) * C / (beta*E - A) * E;
+    ## Dr = D + C / (beta*E - A) * B;
+  endif
+
+endfunction